TFEB variants and uses thereof

ABSTRACT

The invention refers to TFEB related molecules, as variants, mutants, truncated proteins, chimeras etc. that are constitutively localized in the nucleus of a eukaryote cell. Such molecules have a therapeutic applicability in all of disorders that need of an induction of the cell authophagic/lysosomal system, as lysosomal storage disorders, neurodegenerative diseases, hepatic diseases, muscle diseases and metabolic diseases.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a Division of U.S. patent application Ser.No. 14/003,505, filed Oct. 3, 2013, which is a 371 of PCT/EP2012/053921,filed Mar. 7, 2012, which claims the benefit of U.S. ProvisionalApplication No. 61/449,751, filed Mar. 7, 2011, 61/579,793, filed Dec.23, 2011, and 61/596,485, filed Feb. 8, 2012, the contents of each ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The invention refers to TFEB related molecules, as variants, mutants,truncated proteins, chimeras etc. that are constitutively localized inthe nucleus of a eukaryote cell. Such molecules have a therapeuticapplicability in all of disorders that need of an induction of the cellauthophagic/lysosomal system, as lysosomal storage disorders,neurodegenerative diseases, hepatic diseases, muscle diseases andmetabolic diseases.

BACKGROUND OF THE INVENTION

Autophagy is a catabolic process that relies on the cooperation of twodistinct types of cellular organelles, autophagosomes and lysosomes (1).During starvation the cell expands both compartments to enhancedegradation and recycling processes.

The lysosome maintains cellular homeostasis and mediates a variety ofphysiological processes, including cellular clearance, lipidhomeostasis, energy metabolism, plasma membrane repair, bone remodeling,and pathogen defense. All these processes require an adaptive anddynamic response of the lysosome to environmental cues. Indeed,physiologic cues, such as aging and diet, and pathologic conditions,which include lysosomal storage diseases (LSDs), neurodegenerativediseases, injuries and infections may generate an adaptive response ofthe lysosome (34, 35, 36).

The understanding of the mechanisms that regulate lysosomal function andunderlying lysosomal adaptation is still in an initial phase. A majorplayer in the regulation of lysosomal biogenesis is the basicHelix-Loop-Helix (bHLH) leucine zipper transcription factor, TFEB (2).Among the identified TFEB transcriptional targets are lysosomalhydrolases, which are involved in substrate degradation, lysosomalmembrane proteins that mediate the interaction of the lysosome withother cellular structures, and components of the vacuolar H+-ATPase(vATPase) complex, which participate to lysosomal acidification (37, 2).

WO2010/092112 refers to molecules able to enhance the cellulardegradative pathway acting on the so called CLEAR element; among themTFEB is listed.

SUMMARY OF THE INVENTION

The applicants showed that during starvation the cell activates atranscriptional program that controls major steps of the autophagicpathway, including autophagosome formation, autophagosome-lysosomefusion and substrate degradation. The transcription factor EB (TFEB), apreviously identified master gene for lysosomal biogenesis (2),coordinates this program by driving expression of both autophagy andlysosomal genes.

The applicants found that nuclear localization and activity of TFEB areregulated by specific serine phosphorylations. Similar to starvation,pharmacological or gene mutation based inhibition of specificphosphorylation induces autophagy by activating TFEB. These data unveila novel, kinase-dependent, mechanism involved in the regulation of thelysosomal-autophagic pathway by controlling the biogenesis andpartnership of two cooperating cellular organelles.

Therefore it is an object of the invention herein disclosed a TFEBvariant protein that is constitutively localized in the nucleus of aeukaryote cell. The TFEB variant protein of the invention comprises asubstitution or alteration of a serine residue to render the samephosphorylation insensitive. The ordinary skilled in the art wouldrecognize that other amino acid substitutions, other than tyrosine, canbe made to render the TFEB variant phosphorylation insensitive. Forexample the serine residue can be replaced with a natural amino acid,for example a neutral amino acid as alanine, or unnatural amino acid. ATFEB variant protein that is constitutively localized in the nucleus ofa eukaryote cell comprises mutants, truncated proteins, chimeras ofTFEB.

In a preferred embodiment the TFEB variant protein consists of an aminoacid sequence comprised in Seq. Id No. 2 and wherein the substitution ofa serine residue is at SER 142 and/or at SER 211 of Seq. Id No. 2.Preferably the amino acid sequence comprised in Seq. Id No. 2 is fromaa. 117 to aa. 166 and the substitution of a serine residue is at SER142 of Seq. Id No. 2 (Seq Id No. 4). Alternatively the amino acidsequence essentially consists of Seq. Id No. 2 and the substitution of aserine residue is at SER 142 and/or at SER 211. In a most preferredembodiment the substitution(s) at SER 142 and/or SER 211 of Seq. Id. No.2 are to ALA.

It is another object of the invention the TFEB variant protein as abovedisclosed for medical use.

The TFEB variant protein as above disclosed is advantageously used inthe treatment of a disorder that needs of the induction of the cellauthophagic/lysosomal system, preferably for use in the treatment of anyof the following pathologies: lysosomal storage disorders,neurodegenerative diseases, hepatic diseases, muscle diseases andmetabolic diseases.

Examples of lysosomal storage disorder are: activator deficiency/GM2gangliosidosis, alpha-mannosidosis, aspartylglucosaminuria, cholesterylester storage disease, chronic hexosaminidase A deficiency, cystinosis,Danon disease, Fabry disease, Farber disease, fucosidosis,galactosialidosis, Gaucher disease (including Type I, Type II, and TypeIII), GM1 gangliosidosis (including infantile, late infantile/juvenile,adult/chronic), I-cell disease/mucolipidosis II, infantile free sialicacid storage disease/ISSD, juvenile hexosaminidase A deficiency, Krabbedisease (including infantile onset, late onset), metachromaticleukodystrophy, pseudo-Hurler polydystrohpy/mucolipidosis IIIA, MPS IHurler syndrome, MPS I Scheie syndrome, MPS I Hurler-Scheie syndrome,MPS II Hunter syndrome, Sanfilippo syndrome type A/MPS IIIA, Sanfilipposyndrome type B/MPS IIIB, Morquio type A/MPS IVA, Morquio Type B/MPSIVB, MPS IX hyaluronidase deficiency, Niemann-Pick disease (includingType A, Type B, and Type C), neuronal ceroidlipofuscinoses (includingCLN6 disease, atypical late infantile, late onset variant, earlyjuvenile Baten-Spielmeyer-Vogt/juvenile NCL/CLN3 disease, Finnishvariant late infantile CLN5, Jansky-Bielschowsky disease/late infantileCLN2/TPP1 disease, Kufs/adult-onset NCL/CLN4 disease, northernepilepsy/variant late infantile CLN8, and Santavuori-Haltia/infantileCLN1/PPT disease), beta-mannosidosis, Pompe disease/glycogen storagedisease type II, pycnodysostosis, Sandhoff disease/adult onset/GM2gangliosidosis, Sandhoff disease/GM2 gangliosidosis infantile, Sandhoffdisease/GM2 gangliosidosis juvenile, Schindler disease, Salladisease/sialic acid storage disease, Tay-Sachs/GM2 gangliosidosis,Wolman disease, Multiple Sulfatase Deficiency.

Examples of hepatic diseases are: Alpha1 antitrypsin deficiency andFatty liver disease.

Examples of muscle diseases are: Autophagic Vacuolar Myopathies andX-linked myopathy with excessive autophagy.

Examples of metabolic diseases are: hypercholesterolemy and fatty liverdisease.

Examples of neurodegenerative diseases are: Alzheimer's disease,Parkinson's disease, Huntington's disease, Creutzfeldt-Jakob disease,and spinocerebellar ataxia.

It is a further object of the invention a nucleic acid comprising acoding sequence encoding for the TFEB variant protein as abovedisclosed. Preferably the nucleic acid comprises the sequence of Seq. IdNo. 3.

It is a further object of the invention an expression vector comprisingunder appropriate regulative sequences the nucleic acid as abovedisclosed.

The expression vector of the invention may advantageously be used forgene therapy.

It is a further object of the invention a method for increasing theproduction of endogenous or recombinant lysosomal enzymes in an ex vivocultured cell comprising the steps of: —introducing the nucleic acidaccording or the expression vector as above disclosed in said cell and—allowing the expression of the encoded TFEB variant protein.

It is a further object of the invention a method of treating a disorderby administering to a subject a therapeutically effective amount of theTFEB variant protein as above disclosed, preferably when the disorder isalleviated by the induction of the cell authophagic/lysosomal system.

More preferably the disorder is selected from the group comprisinglysosomal storage disorders, neurodegenerative diseases, hepaticdiseases, muscle diseases and metabolic diseases. Examples of suchdisorders were above provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 TFEB induces autophagy. (A) HeLa cells stably overexpressing TFEBwere transfected with a GFP-LC3 plasmid and treated as indicated.Approximately 100 cells were analyzed in triplicate for each experiment.The graph shows quantification of GFP-positive vesicles. (B-F) Westernblot analysis of LC3 in (B) TFEB-3xflag stable overexpressing (+) andcontrol cells (−). The graph represents the quantification using imageJsoftware analysis of LC3II expression (relative to actin) from threeindependent blots; (C) TFEB stable overexpressing cells, which wereserum and amino acid-starved (Starv) for the indicated time (h=hours),(D-F) cellular lysates isolated from TFEB-RNAi and control cells treatedwith scrambled RNAi (ctr) cultured in (D) normal media, (E) starvedmedia, or (F) starved media supplemented with bafilomycin (4 h; 400 nM).The graph represents the quantification of LC3II expression (relative toactin) from three independent blots and band intensities were quantifiedusing imageJ software analysis. (G) TFEB mRNA levels were analyzed byqPCR using cDNAs prepared from cells transfected with 3 different siRNAoligos targeting TFEB (oligo #1, #2, #3), or with a scrambled siRNAoligo (ctr). (H) Representative confocal images of fixed HeLa cellsstably expressing GFP-mRFP-LC3 transfected with empty (control) or TFEBvector. A minimum of 2000 cells was counted and the values represent theaverage number of vesicles (relative to the control, %) obtained fromthree independent experiments. AL (autolysosomes)=mRFP positive/GFPnegative vesicles; total: mRFP positive vesicles. (All error barsrepresent standard deviations. T-test (unpaired) p value (*)<0.05,(**)<0.01)

FIG. 2 Starvation regulates TFEB nuclear translocation and activity. (A)Scatter Plot graphs displaying the logarithmic value of the fold changedifferences in the relative expression levels of 51 autophagy-relatedgenes in HeLa cells cultured in different conditions. X-axis=controlgroup. Y-axis=treated group. Circles represent genes with increased(red) or decreased (green) fold change. Comparisons were as indicated.(B) Chromatin immunoprecipitation (ChIP) analysis. The histogram showsthe amount of immunoprecipitated DNA as detected by qPCR assay. Valueswere normalized to the input and plotted as relative enrichment over amock control. Experiments were performed in triplicate. (C) qPCRanalysis of TFEB-target gene expression in normal, starved, and inTFEB-siRNA starved cells. GAPDH and HPRT represents housekeeping genes,while ATG10, ATG9A and ATG4D represent control genes (non-TFEB targetgenes). (D-F) HeLa cells stably overexpressing TFEB were left untreatedor nutrient starved for 4 h. (D) Five fields containing 50-100cells/each were analyzed for TFEB nuclear localization. P value(*)=<0.01. (E) Cells were subjected to nuclear/cytosolic fractionationand blotted with Flag antibody. H3 and tubulin were used as nuclear andcytosolic markers, respectively. (F) Nuclear fractions were blotted withFlag and H3 (loading control) antibodies. (G) Western blot analysis ofFlag, tubulin and H3 in nuclear extracts prepared from normal, starvedand starved/stimulated with normal media cells for 1 h (normal) orpretreated with AP-2 (AKT inhibitor), Rapamycin (mTOR inhibitor) andU0126 (MEK inhibitor) 1 h prior to media stimulation. Total extractswere used to verify the efficiency of the inhibitors. (H) qPCR analysisof lysosomal and autophagic genes in TFEB siRNA or TFEB-scrambledcontrol cells transfected with either a constitutive active MEK (caMEK)plasmid or with an empty vector. Starvation was performed whereindicated. (All error bars represent standard deviations. T-test(unpaired) p value (*)<0.05, (**)<0.01)

FIG. 3 Serine phosphorylation regulates TFEB activation. (A) TFEBsubcellular localization in HeLa cells expressing mutated versions ofTFEB-3xFlag, immunostained with Flag antibody. Five fields from threeindependent experiments, containing 50-100 cells each were analyzed. (B)qPCR analysis of TFEB target gene expression 24 h post-transfection withempty, normal and mutant TFEB plasmids. (C, D) Western blot analysis ofLC3II (C) and Lamp1 (D) in protein extracts from HeLa cells transfectedwith equal amounts of empty (pcDNA), TFEB-3xFlag or TFEBS142A-3xFlagvectors. Bafilomycin was added where indicated. Experiments were done intriplicate and the quantification of proteins levels were normalized toactin levels. (E) Analysis of autolysosomes (AL=RFP positive/GFPnegative) in HeLa cells stably expressing GFP-mRFP-LC3 and transfectedwith either pcDNA, Tfeb or Ser-Tfeb for 24 h. Quantification as reportedin FIG. 1H. (F) Western blot analysis using anti-Erk antibody on HeLacells transfected with HA-Erk2 kept and/or TFEB-3xFlag, kept in fullserum or nutrient starved for 4 h and immunoprecipitated with anti-Flagantibody. Lysates were immunoprecipitated with anti-FLAG and blottedwith an anti-Erk antibody. (G) In vitro kinase assay. Recombinantkinases were incubated in the presence of ATP-γ ³²P and of a peptidespanning from amino acid 120 to 170 of TFEB protein (TFEB-S-142) or witha similar peptide in which serine 142 was substituted with alanine(TFEB-A-142). Phosphorylation efficiency (“phosphorylation sensitivity”)was measured as the amount of radioactivity incorporated by thepeptides. (H) HeLa stable clones overexpressing TFEB were transfectedwith siRNA oligonucleotides specific for ERK1/2 or with control siRNA.48 h later cells were left untreated, serum starved or serum and aminoacid (a.a.) starved for 4 h, harvested and subjected to nuclearisolation and Flag immunoblotting. Total lysates were probed with ERKantibody. All error bars represent standard deviations. P value(*)=<0.05.

FIG. 4 In vivo analysis of TFEB-mediated induction of autophagy. (A)Immunofluorescence analysis of GFP-positive vesicles in fed, 16h-fasted, and 24 h-fasted mice. Quantification of vesicles is shown inthe graph. (B) qPCR analysis of TFEB target gene expression in liversamples from fed and fasted animals (n=3; Error bars represent standarddeviations. p value (*)<0.05). Gapdh and Hprt were used as referencegenes. (C, D) Analysis of TFEB subcellular localization in two month-oldwild type mice infected with AAV2/9Tcfeb-HA and fasted 16 h prior tosacrifice. (C) HA-immunofluorescence analysis. The graph showsquantification of nuclear HA signal. 100 transduced cells were countedfor each liver. n=3 mice/group. *=<0.001. (D) Western blot analysis ofHA, Tubulin and H3 in liver specimens subjected to nuclearfractionation. Total liver lysates were probed with an HA antibody toverify comparable transgene expression between fed and fasted animals.(E) Western blot analysis of LC3, actin, p-ERK1/2 and ERK1/2 in liverextracts from mice injected AAV2/9Tcfeb-HA. (F) Western blot analysis ofGFP and DAPI staining in cryopreserved liver slices from 2-month oldGFP-LC3 transgenic mice injected with either AAV-Tcfeb-HA or with salinesolution (control group) and fed ad libitum or fasted for 24 h priorsacrifice. Quantification of GFP-positive vesicles is shown in thegraph. (G) qPCR analysis of both autophagic and lysosomal TFEB-targetgene expression in liver samples isolated from conditional Tcfeb-3xFLAGtransgenic mice (Tcfeb-3xflag;AlbCRE), in which transgene expression isdriven by a liver-specific CRE recombinase (i.e. Albumin-CRE). (H)Western blot analysis of LC3 and actin in liver protein extracts fromAlb-CRE, Tcfeb-3xFlag and Tcfeb-3xFlag;Alb-CRE mice.

FIG. 5 TFEB transient overexpression induces autophagy. (A) HeLa cellswere transiently transfected with a plasmid encoding for flagged TFEBprotein. 48 h after transfection cells were collected, lysed and 10 mgof protein samples were analyzed for LC3, Flag and actinimmunoreactivity. Experiments were performed in triplicate and bandintensities were quantified using imageJ software analysis (Error barsrepresent standard deviations. p value (*)<0.05) (B) COS-7 cells weretransiently transfected with an empty vector or with a TFEB-3xFlagvector. 24 hours later cells were treated for 4 h with lysosomalinhibitors (pepstatin/E64, 10 μg/ml, SIGMA). 10 μg of cell lysates weresubjected to LC3 and actin immunoblotting.

FIG. 6 Induction of autophagy in TcFEB overexpressing MEFs. (A, B)Electron micrograph of MEFs infected with lentivirus expressing TcFEBand control cells. (a) Autophagic structures were observed upon TcFEBexpression, including autophagosomes (AV) and autolysosomes (AL). (B)Formation of early autophagosome. Isolation membrane (arrows)surrounding electron-dense cytoplasmatic material. (C) Quantitation ofnumber of autophagic structure (AV and AL) and (D) of earlyautophagosomes. At least 30 cells/group were analyzed. Error barrepresent SEM; p value (*)<0.05; (***)<0.0001.

FIG. 7 TFEB promotes autophagosome formation. (A) Control and stableTFEB-overexpressing cells were treated with bafilomycin (baf; 12 h 400nM) harvested and subjected to LC3II, Flag and actin immunoblotting. (B)Control and TFEB-overexpressing cells were left untreated or treatedwith 10 μg/ml lysosomal inhibitor pepstatin/E64 for 4 h, lysed andsubjected to LC3, Flag and actin immunoblotting. Experiments wereperformed in triplicate and band intensities were quantified usingimageJ software analysis (Error bars represent standard deviations. pvalue (*)<0.05).

FIG. 8 TFEB increases autophagic proteolysis. Rate of long-lived proteindegradation in TFEB-overexpressing, TFEB-depleted and control cells ineither normal or starved condition. 3-methyl adenine (3MA) was addedwhere indicated (Error bars represent standard deviations. p value(*)<0.05).

FIG. 9 Distribution of the TFEB putative binding elements in thepromoter regions of a subset of autophagy genes. Numbers indicate thedistance of the binding element from the transcription start site (TSS).

FIG. 10 Starvation enhances TFEB activity. Luciferase report assay usinga construct carrying four tandem copies of TFEB binding sites. Bothnormal and TFEB-overexpressing HeLa cells were transfected with anartificial promoter with TFEB binding sites. Both cells types displayedincreased transactivation potential when cultured in starved conditions.(Error bars represent standard deviations p (*)<0.05)

FIG. 11 Starvation induces TFEB nuclear translocation through MAPK. (A)Starvation induces cytosolic TFEB mobility shift and nucleartranslocation. Normal medium; starved medium (4 h); starved+normal,indicates that cell were cultured in starved medium (4 h) andsupplemented with normal medium 1 h prior to harvesting. Cytosolic andnuclear fractions were subjected to Flag immunoblotting. (B) Analysis ofTFEB cellular localization by immunofluorescence in HeLa cells treatedas indicated in FIG. 2G. The graph shows percentage of cells thatdisplay TFEB nuclear localization. Error bars represent standarddeviations. P value (*)<0.05

FIG. 12 TFEB nuclear traslocation is dependent on S142 phosphorylation.(A) HeLa cells expressing TFEB-3xFlag, S142A-3xFlag, S332-3xFlag orS423-3xFlag proteins were subjected to nuclear protein isolation. Equalamounts of nuclear proteins were verified by ponceau staining. (B) HeLacells expressing TFEB-3xFlag, S142A-3xFlag and S142D-3xFlag proteinswere subjected to nuclear protein isolation in normal and in starvedconditions. (C) Flag immunoblotting of cytosolic protein isolated fromHeLa cells expressing TFEB-3xFlag and TFEB-S142A-3xFlag showing that innormal media S142A migrates as lower MW band compared to WT TFEB whilethis shift is not evident anymore in starved conditions. (D) Flagimmunoblotting of cytosolic protein isolated from starved HeLa cellsexpressing TFEB-3xFlag, S142A-3xFlag and S142D-3xFlag showing a reducedshift of TFEB-S142D.

FIG. 13 S142A TFEB mutant displays enhanced activity. HeLa cells stablyoverexpressing GFP-LC3 were transfected with equal amounts of empty,TFEB-3xFlag or S142A-TFEB-3xFlag plasmids and the number ofautophagosomes was quantified. At least ten fields (containing 4-10cells) were analyzed for each point. Experiments were performed intriplicate. Error bars represent standard deviations. p value (*)<0.05.

FIG. 14 Multiple sequence alignment of TFEB-human S142 phosphorylationsite with TFEB paralogues, MITF and relevant TFEB-related familymembers. TFEB_human homologs were identified by BLAST (2.2.17) searchagainst UniProtKB database at ExPASy Proteomics Server. The applicantsremoved the hits with “putative”, “uncharacterized” and “cDNA” keywordsand hits without gene names. Next, the applicants authors aligned theremaining homologs with ClustalW (1.82). The multiple sequence alignmentwas generated by Seaview. The figure shows only a 20 amino acid-longsegment of TFEB_HUMAN sequence aligned with other proteins from TFEB,MITF, TCFEB, TFE3 and TCFE3 families. “sp” stands for SwissProt entry,while “tr” denotes Tremble entry. P19484 is a UniProrKB accession code.TFEB_HUMAN indicates gene name and species name respectively.

FIG. 15 Strategy for TcFEB overexpression in vivo. (A) Representativeimages of cryopreserved liver slices immunostained with anti-HA antibody(to verify viral transduction efficiency). (B) Liver protein extractedfrom Tcfeb-HA injected and control mice were immunoblotted HA and actinantibodies. (C) Generation of a transgenic mouse line for TcFEBconditional overexpression. The map of the transgene vector, before andafter CRE recombinase is illustrated at the top. Representativegenotypes of littermates are shown on the left, while the correspondentliver-specific TFEB overexpression in mouse n4 is shown on the right.

FIG. 16 TFEB overexpression increases the release of lysosomal enzymesin the culture medium of MEFs, NSCs, HeLa, and COS-7 cells. Activitiesof lysosomal enzymes acid phosphatase, beta-galactosidase, andbeta-hexosaminidase were determined in the culture medium and in cellstransfected with either an empty vector or with a TFEB-expressionvector. HeLa, Cos7 cells and mouse embryonic fibroblasts from mousemodels of MLIV (S7), MPSIIIA (S7), and MSD were transfected usingPolyFect Transfection Reagent (Qiagen) or lipofectamine 2000 Reagent(Invitrogen), according to the manufacturer's protocols. TFEB-3xFLAGHeLa stable cell lines (CF7) was previously described (2). The figureshows percentages of enzyme activities released compared to totalactivities.

FIG. 17 TFEB exerts a positive control on lysosomal exocytosis. MPSIIIAMEF Cells were maintained in DMEM supplemented with 10% FBS andpenicillin/streptomycin (normal culture medium). Sub-confluent cellswere transfected using Lipofectamine™ 2000 (Invitrogen) according tomanufacturer's protocols. MPS-IIIA MEFs were co-transfected with aplasmid encoding a tagged sulfamidase (SGSH3xFlag) and either an emptyplasmid or a plasmid encoding TFEB. One day after transfection themedium was replaced with DMEM 0.5% FBS. Two days after transfection theconditioned medium and the pellet were collected for sulfamidaseactivity measurement and the percentage of the enzyme released in themedium calculated.

FIG. 18 Lysosomal stress induces TFEB nuclear translocation.Immunoblotting of proteins extracted from HeLa cells that express TFEB-3x Flag treated with chloroquine (CQ) or Salicylihalamide A (SalA),subjected to nuclear/cytosolic fractionation and blotted with antibodyagainst FLAG to detect TFEB. Histone 3 (H3) and tubulin were used asnuclear and cytosolic markers, respectively. Blots are representative oftriplicate experiments.

FIG. 19 mTORC1 regulates TFEB. (A) Lysosomal stress inhibits mTORsignalling. Immunoblotting of protein extracts isolated from HeLa cellstreated overnight, as indicated. Membranes were probed with antibodiesfor p-T202/Y204-ERK1/2, ERK1/2, p-T389-S6K, and S6K to measure ERK andmTORC1 activities. (B) Torin 1 induces TFEB dephosphorylation andnuclear translocation. FLAG immunoblotting of cytosolic and nuclearfractions isolated from TFEB-3 x FLAG HeLa cells cultured in aminoacid-free media and subsequently stimulated as indicated for at least 3h. Correct subcellular fractionation was verified with H3 and tubulinantibodies. (C, D) Effects and dose-response curves of ERK and mTORinhibitors on TFEB nuclear translocation. TFEB-GFP HeLa cells wereseeded in 384-well plates, incubated for 12 h, and treated with 10different concentrations of the ERK inhibitor U0126 or the mTORinhibitors Rapamycin, Torin 1 and Torin 2 ranging from 2.54 nM to 50 μM.After 3 h at 37° C. in RPMI medium containing one of each of thecompounds, the cells were washed, fixed, and stained with DAPI andphotographed by using confocal automated microscopy (Opera high contentsystem, Perkin Elmer). (C) Representative images of test concentrationsfor each compound. Scale bars represent 30 μm. (D) The graph shows thepercentage of nuclear translocation at the 10 different concentrationsof each compound (in log of the concentration). The EC50 for eachcompound was calculated using Prism software (see Materials and methodsfor details). (E) Amino acids induce TFEB molecular weight shift.Immunoblotting of protein extracts isolated from HEK-293T cellstransfected either TFEB-3xFLAG or with an empty vector were nutrientstarved and stimulated for 50 min with amino acids (a.a.). Antibody usedwere p-T389-S6K, S6K and FLAG. (F) Rag knockdown induces TFEB nucleartranslocation. HeLa cells stably expressing Flag-3 x TFEB were infectedwith lentiviruses encoding a Short hairpin (Sh-) RNA targetingluciferase (control) or RagC and RagD mRNAs. In all, 96 h postinfection, cells were left untreated (N=normal media), starved(S=starved media) or treated with Torin 1 (T=Torin 1) for 4 h and thensubjected to nuclear/cytosolic fractionation. TFEB localization wasdetected with a FLAG antibody, whereas tubulin and H3 were used ascontrols for the cytosolic and nuclear fraction, respectively; levels ofS6K phosphorylation were used to test RagC and RagD knockdownefficiency. (G) mTORC2 does not affect TFEB phosphorylation. Mouseembryonic fibroblasts (MEFs) isolated from Sin1−/− or control embryos(E14.5) were infected with a retrovirus encoding TFEB-3 x FLAG; 48 hpost infection, cells were treated with Torin 1 (T) for 4 h, whereindicated, subjected to nuclear/cytosolic fractionation andimmunoblotted for FLAG, tubulin, and H3.

FIG. 20 mTORC1 phosphorylates TFEB at serine 142 (S142). (A) Torin 1induces S142 dephosphorylation. HeLa cells were treated as indicated andtotal and nuclear extracts were probed with a TFEB p-S142phospho-antibody and with anti-FLAG antibody. (B) Schematicrepresentation of TFEB protein structure with the predicted mTORC1phosphorylation sites and their conservation among vertebrates.Numbering is according to human isoform 1. (C) Sequence conservationscores of the phosphorylation sites and quantitative agreement betweenmTOR consensus motif and the sequence around the phosphorylation sitesof TFEB. (D) S142 and S211 regulate TFEB localization. Flagimmunostaining of TFEB subcellular localization in HeLa cells expressingserine-to-alanine mutated versions of TFEB-3 x Flag. Nuclei were stainedwith DAPI. Values are means of five fields containing at least 50transfected cells. Student's t-test (unpaired) ***P<0.001. Scale barsrepresent 30 μm.

FIG. 21 The lysosome regulates gene expression by TFEB. (A) Chloroquinetreatment inhibits mTORC1 activity in primary hepatocytes. Primaryhepatocytes isolated from 2-month-old Tcfebflox/flox (control) andTcfebflox/flox;Alb-Cre(Tcfeb−/−) mice were left untreated or treatedovernight with Torin 1, U0126, or Chloroquine. Subsequently, cells werelysed and protein extracts were immunoblotted with the indicatedantibodies. (B, C) TFEB mediates the transcriptional response tochloroquine and Torin 1. Quantitative PCR (qPCR) of TFEB target genes inprimary hepatocytes from control (flox/flox) and Tcfeb−/− (flox/flox;alb-Cre) mice. Cells were treated with Chloroquine (left) and Torin 1(right). The expression levels are shown as % increased expression ofthe treated versus the corresponding untreated samples. Values representmeans±s.d. of three independent hepatocyte preparations (threemice/genotype). Student's t-test (two tailed) *P-value≦0.05.

DETAILED DESCRIPTION OF THE INVENTION Materials and Methods Cell Cultureand Media and Drugs and Cellular Treatment

HeLa and COS and HEK-293T cells were purchased from ATCC. Cells werecultured in the following media: (normal) DMEM high glucose supplementedwith 10% FBS; (starvation) HBSS media with Ca and Mg supplemented with10 mM HEPES; (Serum) EBSS supplemented with 20% FBS; (amino acid media)Glucose and serum free DMEM; Drugs treatment: Rapamycin (2.5 mg/ml,SIGMA) 2-4 h otherwise indicated; Bafilomycin, (400 nM, SIGMA) 2-4 h;Insulin (100 ng/ml SIGMA) for 2 h; EGF, FGF (BD biosciences); LIF (100ng/ml; ESGRO, Millipore) 2 h; PMA (1 μg/ml) 2 h. U0126 (MEKi) were usedat 25 mM (Cell Signaling), API2 (AKT inhibitor) were used at 1 mM.Lysosomal inhibitors were pepstatin and E64 (10 mg/ml 4 h SIGMA). Thefollowing drugs were used in the experiments of FIGS. 18-2: Rapamycin(2.5 μM5 μM, otherwise indicated) from SIGMA; Torin1 (250 nM, otherwiseindicated) from TOCRIS; U0126 (50 μM) from Cell Signaling technology;Chloroquine (100 μM) from SIGMA; Salicylihalamide A (40 μM) was a kindgift from Jeff De Brabander (UT Southwestern).

Primary hepatocytes were generated as follow: 2-month-old mice weredeeply anaesthetized with Avertin (240 mg/kg) and perfused first with 25ml of HBSS (Sigma H6648) supplemented with 10 mM HEPES and 0.5 mM EGTAand after with a similar solution containing 100 U/ml of Collagenase(Wako) and 0.05 mg/ml of Trypsin inhibitor (Sigma). Liver wasdissociated in a petri dish, cell pellet was washed in HBSS and platedat density of 5×10⁵ cells/35 mm dish and cultured in William's medium Esupplemented with 10% FBS, 2 mM glutamine, 0.1 mM Insulin, 0.1 mMDexamethasone and pen/strep. The next day, cells were treated asdescribed in the text. Sin1−/− and control MEFs were generated aspreviously described (46) and maintained in DMEM supplemented with 10%FBS, glutamine and pen/strep.

Generation of a Tcfeb^(flox) Mouse Line

The applicants used publicly available embryonic stem (ES) cell clones(http colon double forward slash www dot eucomm dot org trailing slash)in which Tcfeb was targeted by homologous recombination at exons 4 and5. The recombinant ES cell clones were injected into blastocysts, whichwere used to generate a mouse line carrying the engineered allele.Liver-specific KO was generated crossing the Flox/Flox mice with atransgenic line expressing the CRE under the Albumin promoter (ALB-CRE)obtained from the Jackson laboratory. All procedures involving mice wereapproved by the Institutional Animal Care and Use Committee of theBaylor College of Medicine.

Transfection, Plasmids and siRNA

Both plasmids and siRNA were transfected with lipofectamine LTX(Invitrogen) using a reverse transfection protocols. siRNA-transfectedcells were collected after 48 or 72 h. siRNA TFEB were used at 50 nM(Dharmacon), siRNA ERK1/2 were used at 100 nM (Cell Signaling).

Cells were transiently transfected with DNA plasmids pRK5-mycPAT1,pCEP4-TFEB-his, pC1G2-TFEB, and p3 x FLAG-CMVTFEB usinglipofectamine2000 or LTX (Invitrogen) according to the protocol frommanufacturer. Site-direct mutagenesis was performed according to themanufacturer instructions (Stratagene) verifying the correct mutagenesisby sequencing.

Western Blotting

Cells or tissues were solubilized in RIPA buffer supplemented withprotease (ROCHE) and Phosphatase (SIGMA) inhibitors. From 10 to 30micrograms were loaded on 4-12% Bis-Tris gel (NUPAGE, Invitrogen),transferred to PVDF membranes and analyzed by western blot using the ECLmethod (Pierce). The following antibodies were used: LC3 (NovusBiological), FLAG, b-ACTIN, TUBULIN (SIGMA), HA (Covance), H3, ERK1/2,p-ERK1/2, p-AKT, p-70S6K (Cell Signaling), ERK2 (Santa Cruz). Proteinlevels were quantified by using ImageJ software analysis.

Nuclear/Cytosolic Fractionation

Cells were seeded at 50% of confluence in 6 well dishes and serumstarved overnight (ON). Normal medium was added the following day eitherin presence of DMSO or kinase inhibitors. Subcellular fractionation wascarried out as previously reported. Briefly, cells were lysed in 0.5Triton X-100 lysis buffer (50 mM Tris-HCl, 0.5% triton, 137.5 mM NaCl,10% glycerol, 5 mM EDTA supplemented with fresh protease and phosphataseinhibitors. Supernatant represented cytosolic fraction while nuclearpellet was washed twice and lysed in 0.5 Triton X-100 buffer 0.5% SDSand sonicated.

Degradation of Long-Lived Proteins

Sub-confluent cells were incubated with L-U¹⁴C-serine for 20 h andchased for 1 h with cold media to degrade short-lived proteins.Subsequently cells were incubated with either normal media or starvationmedia (eventually in the presence of 3-MA) for 4 h. The rate oflong-lived protein degradation was calculated from the ratio of solubleradioactivity in the media to that insoluble in the acid-precipitablecell pellet.

RNA Extraction, Reverse Transcription, ChIP and Quantitative PCR

Total RNA was extracted from tissues using TRIzol (Invitrogen) or fromcells using RNAesy column (Qiagen). Reverse transcription was performedusing TaqMan reverse transcription reagents (Applied Biosystems).Lysosomal and autophagic gene specific primers were previouslyreported². Autophagy gene primers and mouse primers were purchased fromSABiosciences. Fold change calculations were calculated usingSABiosciences' online data analysis website (http colon double forwardslash www dot sabiosciences dot com forward slash per forward slasharrayanalysis dot php) which uses the DDC_(t) method. In brief, theaverage of the most stable housekeeping genes (GAPDH, ACTB, B2M, RPL13A,HPRT and Cyclophillin) were used as “normalizer” genes to calculate theDC_(t) value. Next, the DDC_(t) value is calculated between the“control” group and the “experimental” group. Lastly, the fold change iscalculated using 2^((−DDCt)). Biological replicates were grouped toallow calculating the fold change values. Unpaired T-Test was used tocalculate statistical significance. Asterisks in the graph indicate thatthe P-value was <0.05.

Protein Kinase Prediction

Applicants used five methods including CrPhos0.8, GPS-2.1,PhosphoMotifFinder, Networkin and PHOSIDA using the default parameters(15-19). They further filtered CrPhos0.8 and GPS-2.1 predictionsaccording to their confidence scores. For the former, we took intoaccount the predictions with a false positive rate (FPR) equals or lessthan 30%. For the latter, they considered the predictions with scoreequals or higher than 5. GPS-2.1 scores were calculated as thedifference between actual score and threshold values. We took all thepredictions from other three methods. In the case of Networkin, wecombined predictions from both Networkin and Networkin 2. Each methoddescribes the kinases associated by S142 site in a different kinaseclassification, which simply involves four hierarchical levels: kinasegroup, kinase family, kinase subfamily and kinase itself. To obtain ageneral consensus in each hierarchical level, we classified eachprediction in these four hierarchical levels, if the predictions werenot already classified in that manner. They searched for the missingclassifications at the http colon double forward slash kinase dot orgforward slash kinbase database under vertebrate Glade and human species.Consensus in each classification is found according to the majority votein each classification.

In Vitro Kinase Assay

TFEB-S-142: aa. o 117-166 of Seq Id No. 2:PPPAASPGVRAGHVLSSSAGNSAPNSPMAMLHIGSNPERELDDVIDNIMR and TFEB-A-142: SeqId No. 4, corresponding to aa. of 117-166 of Seq Id No. 2 where Ser 142was substituted with Ala (bold):PPPAASPGVRAGHVLSSSAGNSAPNAPMAMLHIGSNPERELDDVIDNIMR were synthesized byGENESCRIPT corp. The test peptides TFEB-A-142 and TFEB-S-142 were madeup to 1 mM in 50 mM HEPES pH7. There appeared to be no issue withdissolution. The kinase assay was performed at room temperature for 40minutes at 200 μM ATP and 100 μM of each peptide, using Millipore'sstandard radiometric assay. All protein kinases were used at theirstandard KinaseProfiler™ assay concentration. Following incubation, allassays were stopped by the addition of acid and an aliquot spotted ontoP30 and Filtermat A to separate products. All tests were carried out intriplicate, and the usual substrate for each protein kinase included asa control.In Vivo Gene Delivery

The mice were housed in the transgenic mouse facility of Baylor Collegeof Medicine (Houston, Tex., USA). GFP-LC3 transgenic mice were a kindgift of N. Mizushima. C57B6 female mice (4 weeks old) were used, if nototherwise specified. The AAV vector was produced by the TIGEM AAV VectorCore Facility. Briefly, the mouse TFEB (TcFEB) coding sequence wascloned into the pAAV2.1-CMV-GFP plasmid by replacing the GFP sequenceand fused in frame with a HA tag. The resulting pAAV2.1-CMV-TcFEB-HA wasthen triple transfected in sub-confluent 293 cells along with thepAd-Helper and the pack2/9 packaging plasmids. The recombinant AAV2/9vectors were purified by two rounds of CsCl. Vector titers, expressed asgenome copies (GC/mL), were assessed by both PCR quantification usingTaqMan (Perkin-Elmer, Life and Analytical Sciences, Waltham, Mass.) andby dot blot analysis. Each mouse was retro-orbital injected with1.25×10¹¹ viral particle and sacrificed after 3 weeks. Starved mice werefood-deprived for 16 h when analyzed for gene expression, or for 24 hwhen analyzed for GFP-LC3 dots number.

Histology and Immunofluorescence

Liver samples were collected and fixed overnight in 4% paraformaldehydein PBS. After cryoprotection in 10 and 30% sucrose in PBS, the specimenswere frozen in OCT (Sakura Finetech, Torrance, Calif.) and sectioned 30μm thick. Images were taken on an Axioplan2 (Zeiss, Thorwood, N.Y.). Forimmunofluorescence, slices were blocked for 2 h at RT in 2.5% BSA inPBS+0.1% Triton X-100. After blocking, specimens were incubated for 20 hwith the primary antibody and, after 3× washes in PBS+0.05% TX-100, for3 h with secondary antibodies conjugated either with Alexafluor 488 orAlexafluor 555 (Invitrogen). For immunohistochemistry analyses of HA theavidin-biotin complex (ABC) method was used (Vectastain Elite ABC kit).Anti-GFP was from Abcam; (dilution 1:500)

Electron Microscopy

Control and TFEB-overexpressing cells were washed with PBS, and fixed in1% glutaraldehyde dissolved in 0.2 M Hepes buffer (pH 7.4) for 30 min atroom temperature. The cells were then postfixed for 2 h in OsO4. Afterdehydration in graded series of ethanol, the cells were embedded in Epon812 (Fluka) and polymerized at 60° C. for 72 h. Thin sections were cutat the Leica EM UC6, counterstained with uranyl acetate and leadcitrate. EM images were acquired from thin sections using a PhilipsTecnai-12 electron microscope equipped with an ULTRA VIEW CCD digitalcamera (Philips, Eindhoven, The Netherlands). Quantification ofvacuolization was performed using the AnalySIS software (Soft ImagingSystems GmbH, Munster, Germany). Selection of cells for quantificationwas based on their suitability for stereologic analysis, i.e. only cellssectioned through their central region (detected on the basis of thepresence of Golgi membranes) were analyzed.

Animal Models

All procedures involving mice were approved by the Institutional AnimalCareand Use Committee of the Baylor College of Medicine. GFP-LC3transgenic line was described previously. Tissue specific overexpressionof Tcfeb was generated as follows: Tcfeb-3xFlag cDNA was inserted aftera CAGCAT cassette [chicken actin promoter (CAG) followed bychloramphenicol acetyltransferase (CAT) cDNA flanked by 2 loxP sites]and used to generate transgenic mice (Baylor College of Medicinetransgenic core). Mice were then crossed with Albumin-CRE (obtain fromthe Jackson laboratory) line. For 48 Starvation protocol the mice werefood deprived for 22 h, subsequently were fed for 2 h and fasted againfor 24 h prior sacrifice.

Enzymatic Activities

Lysosomal enzymes acid phosphatase, beta-galactosidase, andbeta-hexosaminidaseactivities were measured using the appropriatefluorimetric or colorimetric substrates. SGSH activity was measuredfollowing protocols described in Fraldi et al., Hum Mol Gen 2007 (33).

Immunoblotting and Antibodies

The mouse anti-TFEB monoclonal antibody was purchased from My Biosourcecatalogue No. MBS120432. To generate anti-pS142 specific antibodies,rabbits were immunized with the following peptide coupled to KLH:AGNSAPN{pSer}PMAMLHIC. Following the fourth immunization, rabbits weresacrificed and the serum was collected. Non-phosphospecific antibodieswere depleted from the serum by circulation through a column containingthe non-phosphorylated antigene. The phosphospecific antibodies weresubsequently purified using a column containing the phosphorylatedpeptide.

Cells were lysed with M-PER buffer (Thermo) containing protease andphosphatase inhibitors (Sigma); nuclear/cytosolic fractions wereisolated as above described. Proteins were separated by SDS-PAGE(Invitrogen; reduced NuPAGE 4-12% Bis-tris Gel, MES SDS buffer). Ifneeded, the gel was stained using 20 ml Imperial Protein Stain (ThermoFisher) at room temperature for 1 h and de-stained with water.Immunoblotting analysis was performed by transferring the protein onto anitrocellulose membrane with an I-Blot (Invitrogen). The membrane wasblocked with 5% non-fat milk in TBS-T buffer (TBS containing 0.05%Tween-20) and incubated with primary antibodies anti-FLAG andanti-TUBULIN (Sigma; 1:2000), anti-H3 (Cell Signaling; 1:10 000) at roomtemperature for 2 h whereas the following antibodies were incubated ONin 5% BSA: anti-TFEB (My Biosource; 1:1000), anti-P TFEB (1:1000)ERK1/2, p-ERK1/2, p-P70S6K, P70S6K (Cell Signaling; 1:1000). Themembrane was washed three times with TBS-T buffer and incubated withalkaline phosphatase-conjugated IgG (Promega; 0.2 mg/ml) at roomtemperature for 1 h. The membrane was washed three times with TBS bufferand the expressed proteins were visualized by adding 10 ml Western BlueStabilized Substrate (Promega).

High Content Nuclear Translocation Assay

TFEB-GFP cells were seeded in 384-well plates, incubated for 12 hours,and treated with ten different concentrations (50000 nM, 16666.66 nM,5555.55 nM, 1851.85 nM, 617.28 nM, 205.76 nM, 68.58 nM, 22.86 nM, 22.86nM, 7.62 nM, and 2.54 nM) of ERK inhibitor U0126 (Sigma-Aldrich) andmTOR inhibitors Rapamycin (Sigma-Aldrich), Torin 1 (Biomarin), and Torin2 (Biomarin). After 3 hours at 37° C. in RPMI medium cells were washed,fixed, and stained with DAPI. For the acquisition of the images, tenpictures per each well of the 384-well plate were taken by usingconfocal automated microscopy (Opera high content system, Perkin Elmer).A dedicated script was developed to perform the analysis of TFEBlocalization on the different images (Acapella software, Perkin Elmer).The script calculates the ratio value resulting from the averageintensity of nuclear TFEB-GFP fluorescence divided by the average of thecytosolic intensity of TFEB-GFP fluorescence. The results werenormalized using negative (RPMI medium) and positive (HBSS starvation)control samples in the same plate. The data are represented by thepercentage of nuclear translocation at the different concentrations ofeach compound using Prism software (GraphPad software). The EC50 foreach compound was calculated using non-linear regression fitting (Prismsoftware).

Results

TFEB Induces Autophagy

(Macro)autophagy is an evolutionary conserved mechanism that targetsintracytoplasmic material to lysosomes, thus providing energy supplyduring nutrient starvation (1, 3). Autophagy activation duringstarvation is regulated by mTOR, whose activity is dependent on cellularenergy needs.

As autophagy is the result of a tight partnership between autophagosomesand lysosomes (1), applicants tested whether TFEB, a transcriptionfactor that controls lysosomal biogenesis, regulated autophagy. As TFEBexerts a positive control on lysosomal biogenesis and function (2) andon lysosomal exocytosis (FIGS. 16 and 17), one would expect that TFEBoverexpression should decrease the number of autophagosomes due to theirincreased degradation by the lysosomes. Surprisingly, stable TFEBoverexpression in HeLa cells increased significantly the number ofautophagosomes, as determined by using the LC3 marker, whichspecifically associates with autophagosomes (4-7) (FIGS. 1 a,b). Similardata were obtained by transient overexpression of TFEB in HeLa and Coscells (FIG. 5). An increase in the number of autophagosomes was alsodetected by electron microscopy on mouse embryonic fibroblast (MEFs)infected with a lentivirus overexpressing TFEB (FIG. 6). This increasepersisted in cells treated with lysosomal inhibitors ofautophagosome/LC3II degradation bafilomycin and pepstatin/E64 (8),indicating that TFEB activates the formation of autophagosomes (FIG. 1 aand FIG. 7). Nutrient starvation did not further increase the number ofautophagosomes in TFEB-overexpressing cells (FIGS. 1 a,c), suggesting asaturating effect of TFEB overexpression on autophagy and raising thepossibility that TFEB may be an important mediator of starvation-inducedautophagy.

Consistent with these findings, RNA interference (RNAi) of TFEB in HeLacells resulted in decreased levels of LC3II both in normal and starvedconditions, either in the presence or absence of bafilomycin (FIGS. 1d-f). Notably, the decrease of LC3II correlated with the levels of TFEBdownregulation achieved by the different RNAi oligos, demonstrating thespecificity of the assay (FIG. 1 g). These gain and loss of functiondata suggest that the biogeneses of autophagosomes and lysosomes areco-regulated by TFEB. Applicants next measured the rate of delivery ofautophagosome to lysosome using an RFP-GFP tandem tagged LC3 protein(9), which discriminates early autophagic organelles(GFP-positive/mRFP-positive) from acidified autolysosomes(GFP-negative/mRFP-positive), as the GFP signal (but not the mRFP) isquenched inside acidic compartments (9). They found that the number ofautophagolysosomes was higher in TFEB overexpressing cells compared tocontrol cells, indicating that TFEB promotes autophagosome-lysosomefusion, thus enhancing the autophagic flux (FIG. 1 h). Functionalevidence of TFEB role in the regulation of autophagy came from theobservation that degradation of long-lived proteins was enhanced by TFEBoverexpression, and reduced by TFEB knock-down. This enhancement wasabolished by the autophagy inhibitor 3-methyl adenine (3-MA)(10) (FIG.8).

To test whether TFEB regulated the expression of autophagy genes,applicants analyzed the mRNA levels of a group of 51 genes reported tobe involved in several steps of the autophagic pathway (1, 12, 13). Theyobserved that the enhancement of the expression levels of autophagygenes in cells overexpressing TFEB was very similar to the one obtainedduring starvation (HeLa cells 4 h in EBSS media) (Pearson correlation: rvalue=0.42; pvalue=0.001), while they were downregulated after TFEBsilencing (FIG. 2 a and Tables 1 and 2). Among them the expression ofUVRAG, WIPI, MAPLC3B, SQSTM1, VPS11, VPS18 and ATG9B was mostsignificantly affected by TFEB overexpression (Tables 1 and 2). Thesegenes are known to play a role in different steps of autophagy andappeared to be direct targets of TFEB, as they carry at least one CLEARsite (2) in their promoters (FIG. 9). Interestingly, VPS11, VPS18 andUVRAG play roles in autophagosome delivery to lysosomes (14), consistentwith the observation of a significant enhancement oflysosome-autophagosome fusion in cells overexpressing TFEB.

These data indicate that TFEB is involved in the transcriptionalregulation of starvation-induced autophagy. This conclusion is stronglybolstered by the following observations. First, the luciferase reporterassay (2) showed that starvation enhanced the effects of TFEB on targetgene transcription (FIG. 10). Second, the expression of TFEB directtargets was upregulated in starved cells and this upregulation wasinhibited by TFEB silencing (FIGS. 2 a,c).

Starvation Regulates TFEB Nuclear Translocation and Activity

To identify the mechanism of starvation-induced activation of TFEBapplicants analyzed its subcellular localization and post-translationalmodifications in starved cells. In normal conditions TFEB is localizedto the cytoplasm (2). They observed that nutrient starvation (EBSSmedia) rapidly induced TFEB nuclear translocation (FIGS. 2 d,e), andthat cytosolic TFEB from starved cells appeared to have a lowermolecular weight compared to that of normally fed cells, as revealed bywestern blot analysis (FIG. 11 a). This molecular weight shift occurredrapidly but transiently and was abolished within 1 h after re-addingnormal media to starved cells, concomitant with a decrease of nuclearTFEB (FIG. 11 a). By supplementing EBSS media either with serum, aminoacids or growth factors (i.e. insulin or EGF) applicants observed asignificant inhibition of TFEB nuclear translocation compared to starvedmedia alone (FIG. 2 f). Almost no effect was observed when EBSS wassupplemented with cytokines (i.e. INF or LIF) (FIG. 2 f), suggestingthat activation of TFEB is a process regulated by a signaling mechanism,which is sensitive to nutrient and growth factors. Applicants stimulatedstarved cells with normal medium supplemented with drugs inhibiting themTOR (Rapamycin), PI3K-AKT (Triciribin) and MEK (U0126) kinases.MEKi-inhibition resulted in TFEB nuclear localization, at level similarto starvation, while AKT and mTOR inhibition had no effect (FIG. 2 g andFIG. 11 b). These data suggest that TFEB activity is regulated by MAPkinase, uncovering an unexpected role of this signaling pathway in theregulation of starvation-induced autophagy. Furthermore, the expressionof a constitutively active MEK (caMEK) in HeLa cells resulted indownregulation of TFEB target gene expression during starvation, thusmimicking the effect of TFEB knockdown (FIG. 2 h), while caMEKoverexpression in TFEB-depleted cells had no effect on the expression ofTFEB target genes (FIG. 2 h).

Serine Phosporylation Regulates TFEB Activation

To analyze more in detail the relationship between MAPK signaling andTFEB applicants performed a mass-spectrometry analysis and identified atleast three serines (i.e. S142, S332, and S402) that were phosphorylatedin nutrient rich medium but not in starved medium. They mutated each ofthese three serines to alanines to abolish phosphorylation. Mutant TFEBproteins were individually expressed into HeLa cells and TFEB nucleartranslocation analyzed. The TFEB(S142A) mutant showed a significantlyincreased nuclear localization compared to TFEB(WT), TFEB(S332A) andTFEB(S402A) (FIG. 3 a and FIG. 12 a). Conversely the phospho-mimeticmutant (TFEB S142D) was unable to translocate into the nucleus uponnutrient starvation (FIG. 12 b). The S142A TFEB mutant migrates at lowermolecular weight in normal but not in starved media, while the S142Dmutant displayed a reduced shift during starvation compared to WT TFEB(FIG. 12 c,d), further demonstrating that S142 is phosphorylated innormal but not in starved media. The expression of TFEB(S142A) resultedin increased expression levels of TFEB target genes compared toTFEB(WT), TFEB(S332A) and TFEB(S402A) (FIG. 3 b). Consistently,TFEB(S142A) caused a stronger induction of the autophagic/lysosomalsystem, compared to wt TFEB, as demonstrated by the increased number ofautophagosomes (FIG. 3 c and FIG. 13), lysosomes (FIG. 3 d) andautophagolysosomes (FIG. 3 e). Thus, TFEB nuclear translocation andactivation are regulated by the phosphorylation of serine 142.

To identify the specific kinase responsible for the phosphorylation ofserine 142, applicants performed bioinformatic analyses using methodsthat are based on computational models built upon a set ofexperimentally validated phosphorylation sites (15-19) (see methods fordetails). Consistently with previous results, they identified theserine-specific Extracellular Regulated Kinases (ERKs) as thetop-ranking candidates for the phosphorylation of serine 142 (Table 3).Interestingly, serine 142 is highly conserved in other members of theHLH-leucine zipper gene family, such as the Microphthalmia TranscriptionFactor (MITF) (FIG. 14), where it was found to be phosphorylated by ERK2(20). Further evidence of ERK2-mediated TFEB phosphorylation came fromERK2-TFEB co-immunoprecipitation (FIG. 3 f) in normal but not in starvedmedia Furthermore siRNA-mediated knock-down of ERK1/2 proteins inducedTFEB nuclear translocation to a similar extent as nutrient starvation(FIG. 3 h).

In Vivo Analysis of TFEB-Mediated Induction of Autophagy

Applicants analyzed the physiological relevance of TFEB-mediated controlof the lysosomal/autophagic pathway in vivo in GFP-LC3 transgenic mice(11). They focused studies on the liver, due to the reported autophagicresponse observed in liver upon nutrient depletion. In liver, the numberof GFP-positive vesicles started to increase after 24 hrs of fasting,and peaked at 48 hrs (see mat and methods for 48 h starvation protocol)(FIG. 4 a), while the transcriptional induction of both autophagic andlysosomal TFEB target genes was evident after 16 hrs of fasting (FIG. 4b). Therefore, transcriptional activation precedes autophagosomeformation in vivo. Importantly, at 16 hrs of fasting the sub-cellularlocalization of TFEB was completely nuclear (FIGS. 4 c,d) and the levelof ERK phosphorylation was reduced compared to fed animals (FIG. 4 e),indicating that starvation regulates TFEB activity in vivo, similarly towhat was observed in cultured cells.

Applicants evaluated if TFEB was sufficient to induce autophagy in vivousing both viral- and transgene-mediated TFEB overexpression. GFP-LC3transgenic mice (11) were injected systemically with an adeno-associatedviral (AAV) vector containing the murine TcfebcDNA tagged with an HAepitope (AAV 2/9-Tcfeb-HA) (FIGS. 15 a,b). Liver specimens fromTcfeb-injected animals showed a significant increase in the number ofGFP positive vesicles, and this increase was further enhanced bystarvation (FIGS. 4 e,f). In addition, liver samples from conditionalTcfeb-3xFLAG transgenic mice, in which transgene expression is driven bya liver-specific CRE recombinase (i.e. Albumin-CRE) (FIG. 15 c),displayed a significant increase in the expression of lysosomal andautophagic genes and in the number of autophagosomes compared to controllittermates (FIGS. 4 g,h). Together, these data point to an importantrole of TFEB in the transcriptional regulation of starvation-inducedautophagy.

TORC1 Regulates TFEB Subcellular Localization

TFEB subcellular localization was then analysed in HeLa and HEK-293Tcells transiently transfected with a TFEB-3 x FLAG plasmid and treatedovernight with inhibitors of lysosomal function. These treatmentsincluded the use of chloroquine, an inhibitor of the lysosomal pHgradient, and Salicylihalamide A (Sa1A) a selective inhibitor of thev-ATPase (38). Immunoblotting performed after nuclear/cytoplasmicfractionation revealed that also lysosomal stress induced nucleartranslocation of exogenously expressed TFEB and that again TFEB nuclearaccumulation was associated with a shift of TFEB-3 x FLAG to a lowermolecular weight, suggesting that lysosomal stress may affect TFEBphosphorylation status (FIG. 18).

Based on the observation that mTORC1 resides on the lysosomal membraneand its activity is dependent on both nutrient and lysosomal function(39, 40), applicants postulated that the effects of lysosomal stress onTFEB nuclear translocation may be mediated by mTORC1. Consistent withthis idea, chloroquine or Sa1A inhibited mTORC1 activity as measured bylevel of p-P70S6K, a known mTORC1 substrate (FIG. 19A), (40). Theinvolvement of mTOR appears in contrast with our previous observationthat Rapamycin, a known mTOR inhibitor, did not affect TFEB activity.However, recent data indicate that Rapamycin is a partial inhibitor ofmTOR, as some substrates are still efficiently phosphorylated in thepresence of this drug (41). Therefore, applicants used kinase inhibitorsTorin 1 and Torin 2, which belong to a novel class of molecules thattarget the mTOR catalytic site, thereby completely inhibiting mTORactivity (41, 47, 48).

Applicants stimulated starved cells, in which TFEB is dephosphorylatedand localized to the nucleus, with an amino-acid rich mediumsupplemented with Torin 1 (250 nM), Rapamycin (2.5 μM), or ERK inhibitorU0126 (50 μM). Stimulation of starved cells with nutrients alone induceda significant TFEB molecular weight shift and re-localization to thecytoplasm (FIG. 19B). Nutrient stimulation in the presence of the ERKinhibitor U0126 at a concentration of 50 μM induced only a partial TFEBmolecular weight shift, suggesting that phosphorylation by ERK partiallycontributes to TFEB cytoplasmic localization. Treatment with 2.5 μMRapamycin also resulted in a partial molecular weight shift but did notaffect TFEB subcellular localization (FIG. 19B). However, Torin 1 (250nM) treatment entirely prevented the molecular weight shift induced bynutrients and, in turn, resulted in massive TFEB nuclear accumulation.These data were confirmed in a cell-based high content assay usingstable HeLa cells overexpressing TFEB fused to the green fluorescentprotein (TFEB-GFP). In the assay imaging of treated cells is acquired byan automated confocal microscope (OPERA system) and the analysis ofthose images with Acapella image software calculates the ratio of theaverage of fluorescence intensity of TFEB-GFP between the cytosol andnucleus of the cell (see Materials and methods for details) (FIGS. 19 Cand D). As Torin 1 inhibits both mTORC1 and mTORC2 complexes, applicantsnext evaluated the contribution of each complex to TFEB regulation.Three main observations suggest that TFEB is predominantly regulated bymTORC1: (1) stimulation of starved cells with amino acids, whichactivate mTORC1 but not mTORC2, induced an extensive TFEB molecularweight shift, which is highly suggestive of a phosphorylation event(FIG. 19E); (2) knockdown of RagC and RagD, which mediate amino-acidsignals to mTORC1, caused TFEB nuclear accumulation even in cells keptin full nutrient medium (FIG. 19F); (3) in cells with disrupted mTORC2signalling (Sin1−/− mouse embryonic fibroblasts (MEFs)) (49, 50, 46)TFEB underwent a molecular weight shift and nuclear translocation uponTorin 1 treatment that were similar to control cells (FIG. 19G).

mTORC1 Controls TFEB Subcellular Localization Via the Phosphorylation ofS142

To test whether mTORC1 phosphorylates TFEB at S142, applicants generateda phosphospecific antibody that recognizes TFEB only when phosphorylatedat S142. Using this antibody, applicants authors observed that TFEB wasno longer phosphorylated at S142 in HeLa cells stably overexpressingTFEB-3 x FLAG and cultured in nutrient-depleted media, consistent withapplicants′authors' results above reported (FIG. 20A).

Subsequently, they analysed the levels of S142 phosphoryation in starvedcells supplemented with normal media with or without either Torin 1 orRapamycin. While Torin 1 clearly blunted nutrient-induced S142phosphorylation, rapamycin did not, suggesting that S142 represents arapamycin-resistant mTORC1 site (FIG. 20A). These results clearlydemonstrate that TFEB is an mTOR substrate and that S142 is a keyresidue for the phosphorylation of TFEB also by mTOR.

Recent findings suggest that mTORC1 phosphorylates its target proteinsat multiple sites (42, 43, 44). To identify additional serine residuesthat may be phosphorylated by mTOR, applicants searched for consensusphosphoacceptor motif for mTORC1 (42) in the coding sequence of TFEB(FIGS. 20 B and C). They mutagenized all TFEB amino-acid residues thatwere putative mTORC1 targets into alanines. Then they tested the effectsof each of these mutations on TFEB subcellular localization and foundthat, similarly to S142A, a serine-to-alanine mutation at position 211(S211A) resulted in a constitutive nuclear localization of TFEB (FIG. 20D). Mutations of the other serine residues behaved similarly to thewild-type TFEB (FIG. 20D).

Together, these data indicate that, other than S142, 5211 also plays arole in TFEB subcellular localization and suggest that 5211 representsan additional target site of mTORC1.

The Lysosome Regulates Gene Expression in TFEB

As the interaction of TFEB with mTORC1 controls TFEB nucleartranslocation, applicants tested whether the ability of TFEB to regulategene expression was also influenced by this interaction. The expressionof several lysosomal/autophagic genes that were shown to be targets ofTFEB (37) was tested in primary hepatocytes from a conditional knockoutmouse line in which TFEB was deleted in the liver (Tcfeb^(flox/flox);alb-CRE), and in a control mouse line (Tcfeb^(flox/flox)). Cells weretreated with either chloroquine or Torin 1, or left untreated. Thesetreatments inhibited mTOR as measured by the level of p-S6K, whereas thelevels of P-ERK were unaffected (FIG. 21A). Primary hepatocytes isolatedfrom TFEB conditional knockout mice cultured in regular medium did notshow significant differences in the expression levels of several TFEBtarget genes compared with control hepatocytes. However, while theexpression of TFEB target genes was upregulated in hepatocytes fromcontrol mice after treatment with chloroquine, this upregulation wassignificantly blunted in hepatocytes from TFEB conditional knockout mice(FIG. 21B). Similarly, the transcriptional response upon Torin 1treatment was significantly reduced in hepatocytes from TFEB conditionalknockout mice (FIG. 21C). Together, these results indicate that TFEBplays a key role in the transcriptional response induced by the lysosomevia mTOR.

Both transcriptional-dependent (24, 25) and independent mechanismsregulating autophagy have been described (26, 27). The study identifiesnovel, kinase-dependent, regulatory circuits that control multiplecrucial steps of the autophagic pathway such as autophagosome formation,autophagosome-lysosome fusion and lysosome-mediated degradation of theautophagosomal content. Interestingly, applicants observed that thetranscriptional induction of the autophagic/lysosomal genes precedesautophagosome formation. It could be envisaged that suchtranscriptional-dependent mechanism ensures a more prolonged andsustained activation of autophagy.

Autophagy dysfunction has been linked to several genetic disorders(28-30)), by contrary previous studies showed that enhancement ofautophagy has a therapeutic effect in animal models of neurodegenerativediseases and hepatic fibrosis (29, 31, 32).

The discovery of a novel mechanism that controls, at the transcriptionallevel, the lysosomal-autophagic pathway suggests novel approaches tomodulate cellular clearance in these diseases. Furthermore, it providesa spin-off for therapeutic approaches based on lysosomal enzymes,suggesting new strategies for increasing the productivity of cell linesproducing endogeneous or recombinant lysosomal enzymes (FIGS. 16 and17). Moreover, TFEB overexpression was able to promote substrateclearance and to rescue cellular vacuolization in LSDs (45); thus, theidentification of a phosphorylation-mediated mechanism that regulatesTFEB activity offers a new tool to promote cellular clearance in healthand disease.

TABLE 1 Gene expression changes in response to TFEB overexpression orcell starvation5(Pearson Correlation 0.42) TFEB stable OVEREXPRESSIONCELL STARVATION GENE FOLD GENE FOLD SYMBOL INCREASE SYMBOL INCREASE AKT11.2 AKT1 1.1 AMBRA1 1.2 AMBRA1 1.3 APP 1.4 APP 1.2 ARSA 1.3 ARSA 1.4ATG10 1.1 ATG10 1.0 ATG12 1.2 ATG12 1.2 ATG16L1 −1.2 ATG16L1 −1.5ATG16L2 1.1 ATG16L2 1.0 ATG3 1.2 ATG3 1.0 ATG4A 1.2 ATG4A −1.2 ATG4B 1.3ATG4B 1.1 ATG4C 1.1 ATG4C 1.1 ATG4D 1.6 ATG4D 1.8 ATG5 1.2 ATG5 1.1 ATG71.2 ATG7 1.0 ATG9A 1.1 ATG9A 1.3 ATG9B 5.6 ATG9B 1.8 BAD 1.0 BAD 1.0BAK1 1.4 BAK1 1.0 BAX 1.2 BAX 1.1 BCL2 1.5 BCL2 1.4 BECN1 1.2 BECN1 1.0BID 1.2 BID 1.1 BNIP3 1.1 BNIP3 1.1 CLN3 1.5 CLN3 1.2 CXCR4 1.3 CXCR41.2 DRAM 1.8 DRAM −1.3 EIF2AK3 1.4 EIF2AK3 1.2 EIF4G1 1.3 EIF4G1 −1.2FAM176A 1.6 FAM176A −1.3 GAA 1.3 GAA 1.2 GABARAP 1.1 GABARAP 1.3GABARAPL1 1.0 GABARAPL1 1.2 GABARAPL2 1.1 GABARAPL2 1.0 HGS −1.1 HGS−1.2 HTT 1.0 HTT 1.0 MAP1LC3A 1.1 MAP1LC3A 1.4 MAP1LC3B 1.2 MAP1LC3B 1.2PIK3C3 −1.2 PIK3C3 −1.2 PIK3R4 1.1 PIK3R4 −1.2 PTEN 1.1 PTEN 1.1 RAB241.2 RAB24 1.2 RGS19 1.2 RGS19 −1.2 SNCA 1.6 SNCA −1.2 SQSTM1 2.4 SQSTM11.6 TP53 1.1 TP53 1.0 ULK1 1.1 ULK1 2.0 UVRAG 1.8 UVRAG 2.4 VPS11 1.4VPS11 1.6 VPS18 1.4 VPS18 1.4 WIPI 2.5 WIPI 1.5Pearson product-moment correlation coefficient (PMCC) was obtained bycomparing the gene expression profiles shown, i.e. TFEB stableoverexpression vs. gene expression profiles of starved HeLa cells.

TABLE 2 Gene expression changes in response to TFEB inhibitionusingsiRNA GENE SYMBOL FOLD INCREASE AKT1 −2.1962 AMBRA1 1.1134 APP −1.1769ARSA −2.858 ATG10 1.0389 ATG12 1.0461 ATG16L1 −1.6529 ATG16L2 −1.3333ATG3 1.2702 ATG4A −1.3333 ATG4B −1.244 ATG4C −1.6077 ATG4D −1.1527 ATG5−1.0607 ATG7 −1.6994 ATG9A −1.9793 ATG9B −4.4229 BAK1 1.4489 BAX −1.3803BCL2 −2.3054 BECN1 −1.1769 BID 1.3241 BNIP3 −1.1212 CLN3 −1.4692 CXCR4−1.5529 DRAM −1.1769 EIF2AK3 −1.3996 EIF4G1 −2.3702 ESR1 −1.676 GAA−1.3613 GABARAP 1.4093 GABARAPL1 −1.2016 GABARAPL2 1.3899 HGS −1.5594HTT −1.3899 MAP1LC3A −1.0389 MAP1LC3B −1.4175 PIK3R4 −1.6189 PTEN−1.2702 RAB24 1.3333 SNCA 1.2269 SQSTM1 −1.4093 TP53 −1.279 ULK1 −3.668UVRAG −1.3059 VPS11 −1.84 VPS18 −2.1 WIPI −1.94Down-regulated genes upon siRNA-mediated TFEB knock-down. Fold changerepresents the average of 4 independent experiments. Genes significantlydown-regulated are indicated in red (p<0.05).

TABLE 4 Prediction of S142 phosphorylation using different methodsMETHODS Cutoff Actual prediction for S142 Group Family Subfamily KinaseCrPhos0.8 FPR ≦ 30% MAPK8 CMGC MAPK JNK MAPK8 CrPhos0.8 FPR ≦ 30% MAPK3CMGC MAPK ERK MAPK3 CrPhos0.8 FPR ≦ 30% MAPK1 CMGC MAPK ERK MAPK1CrPhos0.8 FPR ≦ 30% CDK2 CMGC CDK CDK2 CDK2 GPS-2.1 Score ≧ 5CMGC/CDK/CDK5 CMGC CDK CDK5 GPS-2.1 Score ≧ 5 CMGC/CDK/CDK4/CDK4 CMGCCDK CDK4 CDK4 GPS-2.1 Score ≧ 5 CMGC/MAPK/ERK/MAPK1 CMGC MAPK ERK MAPK1GPS-2.1 Score ≧ 5 CMGC/MAPK/ERK/MAPK3 CMGC MAPK ERK MAPK3 GPS-2.1 Score≧ 5 CMGC/MAPK/JNK/MAPK8 CMGC MAPK JNK MAPK8 GPS-2.1 Score ≧ 5CMGC/MAPK/JNK/MAPK10 CMGC MAPK JNK MAPK10 GPS-2.1 Score ≧ 5STE/STE7/MAP2K7 STE STE7 MAP2K7 GPS-2.1 Score ≧ 5 CMGC/MAPK/p38/MAPK12CMGC MAPK p38 MAPK12 PhosphoMotifFinder GSK3 CMGC GSK GSK3PhosphoMotifFinder ERK1 CMGC MAPK ERK MAPK3 PhosphoMotifFinder ERK2 CMGCMAPK ERK MAPK1 PhosphoMotifFinder ERK3 CMGC MAPK ERK MAPK6PhosphoMotifFinder CDK5 CMGC CDK CDK5 CDK5 Networkin p38MAPK/MAPK9 CMGCMAPK JNK MAPK9 Networkin GSK3/GSK3B CMGC GSK GSK3 GSK3B NetworkinCDK5/CDK2 CMGC CDK CDK2 CDK2 networkin 2 CDK2_CDK3/CDK2 CMGC CDK CDK2CDK2 PHOSIDA CK1_group CK1 CK1 PHOSIDA ERK CMGC MAPK ERKResults of the prediction of phosphorylation of S142 using fivedifferent methods. Methods are given in the first column. The secondcolumn indicates confidence score cutoff as described in methods, whenavailable. The third column shows the actual format of predictionobtained by the corresponding method. The next four columns show theprediction in the kinase group, kinase family, kinase subfamily andkinase protein classifications, respectively.

REFERENCES

-   1 He, C. & Klionsky, D. J. Regulation mechanisms and signaling    pathways of autophagy. Annu Rev Genet 43, 67-93 (2009).-   2 Sardiello, M. et al. A gene network regulating lysosomal    biogenesis and function. Science 325, 473-477 (2009).-   3 Lum, J. J. et al. Growth factor regulation of autophagy and cell    survival in the absence of apoptosis. Cell 120, 237-248 (2005).-   4 Klionsky, D. J., Elazar, Z., Seglen, P. O. & Rubinsztein, D. C.    Does bafilomycin A1 block the fusion of autophagosomes with    lysosomes? Autophagy 4, 849-950 (2008).-   5 Xie, Z. & Klionsky, D. J. Autophagosome formation: core machinery    and adaptations. Nat Cell Biol 9, 1102-1109 (2007).-   6 Rubinsztein, D. C. et al. In search of an “autophagomometer”.    Autophagy 5, 585-589 (2009).-   7 Mizushima, N., Yoshimori, T. & Levine, B. Methods in mammalian    autophagy research. Cell 140, 313-326 (2010).-   8 Klionsky, D. J., Cuervo, A. M. & Seglen, P. O. Methods for    monitoring autophagy from yeast to human. Autophagy 3, 181-206    (2007).-   9 Kimura, S., Noda, T. & Yoshimori, T. Dissection of the    autophagosome maturation process by a novel reporter protein, tandem    fluorescent-tagged LC3. Autophagy 3, 452-460 (2007).-   10 Bauvy, C., Meijer, A. J. & Codogno, P. Assaying of autophagic    protein degradation. Methods Enzymol 452, 47-61 (2009).-   11 Mizushima, N., Yamamoto, A., Matsui, M., Yoshimori, T. &    Ohsumi, Y. In vivo analysis of autophagy in response to nutrient    starvation using transgenic mice expressing a fluorescent    autophagosome marker. Mol Biol Cell 15, 1101-1111 (2004).-   12 Mizushima, N. Autophagy: process and function. Genes Dev 21,    2861-2873 (2007).-   13 Behrends, C., Sowa, M. E., Gygi, S. P. & Harper, J. W. Network    organization of the human autophagy system. Nature 466, 68-76    (2010).-   14 Liang, C. et al. Beclin1-binding UVRAG targets the class C Vps    complex to coordinate autophagosome maturation and endocytic    trafficking. Nat Cell Biol 10, 776-787 (2008).-   15 Dang, T. H., Van Leemput, K., Verschoren, A. & Laukens, K.    Prediction of kinase-specific phosphorylation sites using    conditional random fields. Bioinformatics 24, 2857-2864 (2008).-   16 Xue, Y. et al. GPS 2.0, a tool to predict kinase-specific    phosphorylation sites in hierarchy. Mol Cell Proteomics 7, 1598-1608    (2008).-   17 Amanchy, R. et al. A curated compendium of phosphorylation    motifs. Nat Biotechnol 25, 285-286 (2007).-   18 Linding, R. et al. Systematic discovery of in vivo    phosphorylation networks. Cell 129, 1415-1426 (2007).-   19 Gnad, F. et al. PHOSIDA (phosphorylation site database):    management, structural and evolutionary investigation, and    prediction of phosphosites. Genome Biol 8, R250 (2007).-   20 Hemesath, T. J., Price, E. R., Takemoto, C., Badalian, T. &    Fisher, D. E. MAP kinase links the transcription factor    Microphthalmia to c-Kit signalling in melanocytes. Nature 391,    298-301 (1998).-   21 Kolch, W. Coordinating ERK/MAPK signalling through scaffolds and    inhibitors. Nat Rev Mol Cell Biol 6, 827-837 (2005).-   22 Corcelle, E. et al. Disruption of autophagy at the maturation    step by the carcinogen lindane is associated with the sustained    mitogen-activated protein kinase/extracellular signal-regulated    kinase activity. Cancer Res 66, 6861-6870 (2006).-   23 Lipinski, M. M. et al. A genome-wide siRNA screen reveals    multiple mTORC1 independent signaling pathways regulating autophagy    under normal nutritional conditions. Dev Cell 18, 1041-1052 (2010).-   24 Zhao, J. et al. FoxO3 coordinately activates protein degradation    by the autophagic/lysosomal and proteasomal pathways in atrophying    muscle cells. Cell Metab 6, 472-483 (2007).-   25 Mammucari, C. et al. FoxO3 controls autophagy in skeletal muscle    in vivo. Cell Metab 6, 458-471 (2007).-   26 He, C. & Levine, B. The Beclin 1 interactome. Curr Opin Cell Biol    22, 140-149 (2010).-   27 Neufeld, T. P. TOR-dependent control of autophagy: biting the    hand that feeds. Curr Opin Cell Biol 22, 157-168 (2010).-   28 Wong, E. & Cuervo, A. M. Autophagy gone awry in neurodegenerative    diseases. Nat Neurosci 13, 805-811 (2010).-   29 Levine, B. & Kroemer, G. Autophagy in the pathogenesis of    disease. Cell 132, 27-42 (2008).-   30 Settembre, C. et al. A block of autophagy in lysosomal storage    disorders. Hum Mol Genet 17, 119-129 (2008).-   31 Hidvegi, T. et al. An autophagy-enhancing drug promotes    degradation of mutant alpha1-antitrypsin Z and reduces hepatic    fibrosis. Science 329, 229-232 (2010).-   32 Rubinsztein, D. C., Gestwicki, J. E., Murphy, L. O. &    Klionsky, D. J. Potential therapeutic applications of autophagy. Nat    Rev Drug Discov 6, 304-312 (2007).-   33 Fraldi, A., Hemsley, K., Crawley, A., Lombardi, A., Lau, A.,    Sutherland, L., Auricchio, A., Ballabio, A. and Hopwood, J. J.    Functional correction of CNS lesions in an MPS-IIIA mouse model by    intracerebral AAV-mediated delivery of sulfamidase and SUMF1 genes.    Hum Mol Genet, 16, 2693-702 (2007).-   34 Ballabio A, Gieselmann V (2009) Lysosomal disorders: from storage    to cellular damage. Biochim Biophys Acta 1793: 684-696-   35 Luzio J P, Pryor P R, Bright N A (2007) Lysosomes: fusion and    function. Nat Rev Mol Cell Biol 8: 622-632-   36 Saftig P, Klumperman J (2009) Lysosome biogenesis and lysosomal    membrane proteins: trafficking meets function. Nat Rev Mol Cell Biol    10: 623-635-   37 Palmieri M, Impey S, Kang H, di Ronza A, Pelz C, Sardiello M,    Ballabio A (2011) Characterization of the CLEAR network reveals an    integrated control of cellular clearance pathways. Hum Mol Genet 20:    3852-3866-   38 Xie X S, Padron D, Liao X, Wang J, Roth M G, De Brabander J    K (2004) Salicylihalamide A inhibits the V0 sector of the V-ATPase    through a mechanism distinct from bafilomycin A1. J Biol Chem 279:    19755-19763-   39 Sancak Y, Bar-Peled L, Zoncu R, Markhard A L, Nada S, Sabatini D    M (2010) Ragulator-Rag complex targets mTORC1 to the lysosomal    surface and is necessary for its activation by amino acids. Cell    141: 290-303-   40 Zoncu R, Bar-Peled L, Efeyan A, Wang S, Sancak Y, Sabatini D M    (2011a) mTORC1 senses lysosomal amino acids through an inside-out    mechanism that requires the vacuolar H-ATPase. Science 334: 678-683-   41 Thoreen C C, Kang S A, Chang J W, Liu Q, Zhang J, Gao Y,    Reichling L J, Sim T, Sabatini D M, Gray N S (2009) An    ATP-competitive mammalian target of rapamycin inhibitor reveals    rapamycin-resistant functions of mTORC1. J Biol Chem 284: 8023-8032-   42 Hsu P P, Kang S A, Rameseder J, Zhang Y, Ottina K A, Lim D,    Peterson T R, Choi Y, Gray N S, Yaffe M B, Marto J A, Sabatini D    M (2011) The mTOR-regulated phosphoproteome reveals a mechanism of    mTORC1-mediated inhibition of growth factor signaling. Science 332:    1317-1322-   43 Peterson T R, Sengupta S S, Harris T E, Carmack A E, Kang S A,    Balderas E, Guertin D A, Madden K L, Carpenter A E, Finck B N,    Sabatini D M (2011) mTOR complex 1 regulates lipin 1 localization to    control the SREBP pathway. Cell 146: 408-420-   44 Yu Y, Yoon S O, Poulogiannis G, Yang Q, Ma X M, Villen J, Kubica    N, Hoffman G R, Cantley L C, Gygi S P, Blenis J (2011)    Phosphoproteomic analysis identifies Grb10 as an mTORC1 substrate    that negatively regulates insulin signaling. Science 332: 1322-1326-   45 Medina D L, Fraldi A, Bouche V, Annunziata F, Mansueto G,    Spampanato C, Puri C, Pignata A, Martina J A, Sardiello M, Palmieri    M, Polishchuk R, Puertollano R, Ballabio A (2011) Transcriptional    activation of lysosomal exocytosis promotes cellular clearance. Dev    Cell 21: 421-430-   46 Jacinto E, Facchinetti V, Liu D, Soto N, Wei S, Jung S Y, Huang    Q, Qin J, Su B (2006) SIN1/MIP1 maintains rictor-mTOR complex    integrity and regulates Akt phosphorylation and substrate    specificity. Cell 127: 125-137-   47 Feldman M E, Apsel B, Uotila A, Loewith R, Knight Z A, Ruggero D,    Shokat K M (2009) Active-site inhibitors of mTOR target    rapamycin-resistant outputs of mTORC1 and mTORC2. PLoS Biol 7: e38-   48 Garcia-Martinez J M, Moran J, Clarke R G, Gray A, Cosulich S C,    Chresta C M, Alessi D R (2009) Ku-0063794 is a specific inhibitor of    the mammalian target of rapamycin (mTOR). Biochem J 421: 29-42-   49 Frias M A, Thoreen C C, Jaffe J D, Schroder W, Sculley T, Carr S    A, Sabatini D M (2006) mSin1 is necessary for Akt/PKB    phosphorylation, and its isoforms define three distinct mTORC2s.    Curr Biol 16: 1865-1870-   50 Yang Q, Inoki K, Ikenoue T, Guan K L (2006) Identification of    Sin1 as an essential TORC2 component required for complex formation    and kinase activity. Genes & development 20: 2820-2832

The invention claimed is:
 1. A nucleic acid comprising a coding sequenceencoding for a transcription factor EB (TFEB) variant protein, (a)wherein the encoded TFEB variant protein comprises SEQ ID NO: 2, whereinSer is replaced by a non-serine amino acid residue at positions 142and/or 211 of SEQ ID NO: 2; or (b) wherein the encoded TFEB variantprotein consists of amino acid residues 117 to 166 of SEQ ID NO: 2,wherein Ser is replaced by a non-serine amino acid residue at a positioncorresponding to position 142 of SEQ ID NO: 2; and wherein said variantprotein induces autophagy.
 2. The nucleic acid according to claim 1,wherein the non-serine amino acid residue of the encoded TFEB variantprotein is Ala.
 3. The nucleic acid according to claim 1, wherein theencoded TFEB variant protein consists of SEQ ID NO: 2, wherein Ser isreplaced by a non-serine amino acid residue at amino acid residuepositions 142 and/or
 211. 4. The nucleic acid according to claim 1,wherein the encoded TFEB variant protein is according to claim 1, part(a).
 5. The nucleic acid according to claim 1, wherein the encoded TFEBvariant protein is according to claim 1, part (b).
 6. The nucleic acidof claim 1 consisting of a coding sequence encoding for a transcriptionfactor EB (TFEB) variant protein, (a) wherein the encoded TFEB variantprotein comprises SEQ ID NO: 2, wherein Ser is replaced by a non-serineamino acid residue at positions 142 and/or 211 of SEQ ID NO: 2; or (b)wherein the encoded TFEB variant protein consists of amino acid residues117 to 166 of SEQ ID NO: 2, wherein Ser is replaced by a non-serineamino acid residue at a position corresponding to position 142 of SEQ IDNO: 2; and wherein said variant protein induces autophagy.
 7. Thenucleic acid according to claim 6, wherein the non-serine amino acidresidue of the encoded TFEB variant protein is Ala.
 8. An expressionvector comprising, under appropriate regulative sequences, the nucleicacid according to claim 1.